In conventional, inflatable restraining systems used in vehicles, there typically is provided a volume of compressed gas which is released upon collision of the vehicle to expand and thereby inflate a collapsed bag between the vehicle structure and a vehicle occupant. Such a compressed gas is stored in a metal canister which typically is installed in the steering column or dashboard of the vehicle, immediately ahead of the collapsed inflatable bag usually located at the center of the steering wheel or on the dashboard. One of such canisters is illustrated in FIG. 5 of the accompanying drawings and will been seen to include an elongated, cylindrical body section 20 merging at its ends into annular rounded portions 21 and 22 providing a pair of axially disposed end openings. The end openings are closed by a pair of cup-shaped metallic plugs 23 and 24 usually welded to the main body section of the canister. Mounted in one of such end plugs and intended to be positioned adjacent an opening of the inflatable bag, is a propellant charge adapted to detonate and thus rupture an opening in the plug to release the stored gas within the canister. In the operation of the restraining system, upon one or more of various sensors installed at points about the periphery of the vehicle sensing a collision condition of the vehicle, an electrical signal is generated to cause the propellant charge to detonate and thus rupture a wall section of the end plug adjacent the inflatable bag.
Upon such rupture, the stored gas in the canister releases through the ruptured plug wall and inflates the bag to provide a cushioning barrier between the vehicle occupant and the vehicle structure. Another of such canisters is illustrated and described in U.S. Pat. No. 3,806,153 to James T. Johnson.
In the manufacture of such canisters, the main body sections thereof are formed from desired lengths of tubular stock having the annular, rounded end portions thereof formed by swaging or other suitable methods. The end plugs preferably are formed by stamping and are secured in the end openings by welding. One of such plugs is provided with an opening for injecting a gas under pressure into the canister. After the canister components have been formed and assembled, a gas pressure sensor is installed in the end plug provided with the gas filling opening, the propellant charge is installed in the opposite end plug and the canister is filled with gas and sealed.
In filling the type of canister described with a gas under pressure, it has been the prior practice to first insert a narrow filler tube into the end plug of the canister provided with the gas filling opening, between the side wall of the plug and the installed sensor, communicating with the interior of the canister through the opening in the bottom wall of the plug and engaging the bottom wall of the plug about the periphery of the opening in the bottom wall in sealing engagement. Then, while maintaining such sealing engagement between the end of the filler tube and the bottom wall of the canister plug, a gas under high pressure is injected through the filler tube and the plug opening into the canister, a fusible ball or bead is dispensed through the filler tube and deposited in the plug wall opening, a welding rod is extended through the filler tube into contact with the fusible ball seated in the plug wall opening, the welding rod is energized to fuse the ball and thus close the plug wall opening, and the welding rod and filler tube are sequentially retracted to complete the operation.
Such process of filling inflatable bag canisters has been found to be disadvantageous in several respects. The necessity of having to insert the filler tube into the end plug not only requires the filler tube to be fairly narrow in width but further requires the end plug be formed with a sufficiently greater depth to be able to accommodate both the gas leakage sensor and the insertion of the filler tube within the confined space of the end plug. The increased depth requirement of the plug results in having to machine the end plug instead of stamping it which has the effect of substantially increasing the cost of manufacture of the canister. A further disadvantage of such process is in having to position the filler tube with the welding rod extended therethrough into engagement with a fusible ball seated in the plug wall opening, in close proximity to the sensor device, which generates a substantial amount of heat which could result in damage and ultimate malfunction of the sensor. It thus has been found to be desirable to provide an apparatus and method for charging inflatable bag canisters of the type described with a high pressure gas in the range of 3,000 to 10,500 psi which is effective in overcoming such disadvantages of prior art systems and methods for charging such canisters.
Accordingly, it is the principal object of the present invention to provide an improved apparatus for charging canisters used in inflatable restraining systems of vehicles with a gas under high pressure.
Another object of the present invention is to provide an improved apparatus for charging canisters used in inflatable restraining systems of vehicles with a gas under pressure in the range of 3,000 to 10,500 psi.
A further object of the present invention is to provide an improved apparatus for charging an inflatable bag canister of a vehicle restraining system in a manner not interfering with any propellant charge or gas leakage sensor device typically provided on such canisters.
A still further object of the present invention is to provide an apparatus for charging a canister formed with a pair of cup-shaped plugs closing openings at opposite ends of the canister accommodating a propellant charge and a gas leakage sensor, requiring comparatively shallow plug depths, permitting such plugs to be stamped in lieu of having to be machined.
Another object of the present invention is to provide an improved apparatus for charging an inflatable bag canister used in a restraining system of a vehicle which is comparatively simple in design, comparatively easy to manufacture, economical to operate and highly effective in performance.
A further object of the present invention is to provide a novel assembly for sequentially forming a seal about a gas filling opening in an inflatable bag canister used in a vehicle restraining system, injecting a gas under pressure through such opening into the canister while maintaining such seal, and then depositing a fusible ball in such gas filling opening and fusing it to close the opening while continuing to maintain such seal.
A still further object of the present invention is to provide an improved method for charging an inflatable bag canister used in a vehicle inflatable restraining system with a gas under high pressure.
Other objects and advantages of the present invention will become more apparent to those persons having ordinary skill in the art to which the present invention pertains from the accompanying drawings taken in conjunction with the following description.